Building first Grendel- what are common pitfalls.

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  • zcostilla
    Warrior
    • Aug 2017
    • 110

    Building first Grendel- what are common pitfalls.

    -Zac

    Husband, Father, Veteran. Grateful for my redemption.
  • Bigs28
    Chieftain
    • Feb 2016
    • 1786

    #2
    Most common pit fall is that you will want another.

    Comment

    • bigdaddyflo
      Bloodstained
      • Dec 2016
      • 97

      #3
      Here are some of the issues you may have to look out for . . .
      1. Get a barrel and matching headspaced bolt (if your budget allows) or just be certain that the bolt you get will be for the barrel you buy. Type I or type II - and stick with only one type if you do multiple builds.

      2. Test fit everything BEFORE you send it out to get cerakoted (if you go that route)! I had an upper and lower cerakoted and I had problems with the upper - the cam pin would hit the inside of the upper receiver when charging and would hang up. I had to do some "custom fitting" so it wouldn't hit. If I had known this before being sent out to get cerakoted, I would have just replaced the upper receiver with another.

      3. If you are going to be suppressed - get an adjustable gas block!

      4. Some people face the receiver, others don't and say it doesn't do any good. I personally do it just to give my self a piece of mind.

      5. Get good magazines!

      6. I always lap my scope rings too. Nothing like taking a $500 -$1,500 scope out of the rings and have it all dented/bent.

      I personally get the most scope I can get. I'm 50 and my eyes are not the best. If I want to shoot long range, I can! It just leaves my shooting options open.

      Comment

      • pinzgauer
        Warrior
        • Mar 2011
        • 440

        #4
        Don't get sucked into non-SAAMI Chambers and throats. Same for non standard bolt faces.

        Better yet: Save yourself a lot of trouble and buy one of the inexpensive Alexander Arms Barrel and bolts to get started

        Most of the so-called improvements some people push aren't. At best they are fixes to non-existent problems.

        There are other Barrel and both options to consider, but it's a lot harder to sort through which ones are good to go versus not. And if you're just getting started, it's really good to go with a known quantity.

        Comment

        • howl
          Warrior
          • Nov 2015
          • 236

          #5
          I'd want a 2-10x for that range. You don't need a heavy barrel for accuracy, just a good one. People tend to build their ARs up too heavy for field work.

          Comment

          • VASCAR2
            Chieftain
            • Mar 2011
            • 6218

            #6
            I think the biggest concern for the 6.5 Grendel is it’s not fur friendly. The 95 grain V-Max is popular in the 6.5 Grendel for varmint hunting. The only real factory varmint load for the 6.5 Grendel is the 90 grain TNT from Federal. Depending on your terrain you might be able to use 107 grain Sierra Match Kings. I’ve water tested 85 grain Sierra Varmint, 90 grain TNT and 95 grain V-Max. The penetration in water is very similar between all three bullets and the bullets produced roughly the same fragmentation and retained weight.

            A Friend has used a 243 Savage bolt gun on coyotes for years but just recently started using a 20” 6.5 Grendel with hand loaded 85 grain Sierra varmint bullets. My Friend has been very impressed with the 6.5 Grendel ease of use, range and lethality of the 85 grain SV 6.5 Grendel.

            The main concern for optics on my coyote rifle is low light performance matched to the magnification. I have no personal experience with the SWFA 1-6 but it does get good reviews. Sounds like I live straight east of you in SE Illinois. If you’ve never shot a 6.5 Grendel I’d be willing to drive west and let you shoot my 16” and 20” 6.5 Grendels.

            Comment

            • zcostilla
              Warrior
              • Aug 2017
              • 110

              #7
              Originally posted by VASCAR2 View Post
              I think the biggest concern for the 6.5 Grendel is it’s not fur friendly. The 95 grain V-Max is popular in the 6.5 Grendel for varmint hunting. The only real factory varmint load for the 6.5 Grendel is the 90 grain TNT from Federal. Depending on your terrain you might be able to use 107 grain Sierra Match Kings. I’ve water tested 85 grain Sierra Varmint, 90 grain TNT and 95 grain V-Max. The penetration in water is very similar between all three bullets and the bullets produced roughly the same fragmentation and retained weight.

              A Friend has used a 243 Savage bolt gun on coyotes for years but just recently started using a 20” 6.5 Grendel with hand loaded 85 grain Sierra varmint bullets. My Friend has been very impressed with the 6.5 Grendel ease of use, range and lethality of the 85 grain SV 6.5 Grendel.

              The main concern for optics on my coyote rifle is low light performance matched to the magnification. I have no personal experience with the SWFA 1-6 but it does get good reviews. Sounds like I live straight east of you in SE Illinois. If you’ve never shot a 6.5 Grendel I’d be willing to drive west and let you shoot my 16” and 20” 6.5 Grendels.
              @VASCAR2 That’s mighty friendly of you. I live about 20 minutes east of St Louis. I’d like to take you up on your offer sometime.

              All: this is the kind of info I was hoping for. Thanks for the input. Especially the reminder to lap the scope rings. I made that mistake once myself and scratched a good riflescope. So what kind of maga

              I’m torn on the scope. On one hand, I’m a big fan of fixed power scopes for their simplicity and the fact that you generally (but not dogmatically) get better reliability/ruggedness for the same weight (or less weight for the same reliability) with a fixed power scope vs a variable power. If I do get a variable power, it must be first focal plane to be able to get the full benefits of the reticle regardless of magnification.
              -Zac

              Husband, Father, Veteran. Grateful for my redemption.

              Comment

              • grayfox
                Chieftain
                • Jan 2017
                • 4295

                #8
                Couple more ideas for you.
                1. I have both Magpul fixed length rifle stock and adjustable carbines, I standardized on carbine length springs, so in the rifle I use the buffer tube adapter; also I'm using JP Enterprise centerless springs and either Spikes T2 or Kaw valley (T2-4.3 oz) buffer spring/buffer weight - they really smooth out the recoil action and mostly eliminate the Sproing.
                2. I'd recommend nitrided or NiB bcg's, they just add some smoothness.

                These are both minor adds but they're helping me.
                Good shooting!
                (I lived in northern ILL for a while back in the day but moved south to avoid the winters... lol!)
                "Down the floor, out the door, Go Brandon Go!!!!!"

                Comment

                • VASCAR2
                  Chieftain
                  • Mar 2011
                  • 6218

                  #9
                  zcostilla I sent you a private message.

                  Comment

                  • bj139
                    Chieftain
                    • Mar 2017
                    • 1968

                    #10
                    One unusual thing you should be aware of is the Grendel bolt, not the bolt carrier, is longer than a 5.56 bolt.
                    This is to compensate for the .136 bolt face depth while maintaining the 5.56 length firing pin.
                    If you buy a Grendel BCG from Brownells, which I have, it will have a standard length bolt but a shorter firing pin.
                    It works fine.
                    If you buy the group buy bolt from here, which I have also, you can take out your 5.56 bolt from a standard BCG and replace it and your standard firing pin will be fine.
                    The firing pin should not stick out too far or you may have pierced primers.

                    There is at least one thread here discussing this issue.

                    Comment

                    • warp9764
                      Bloodstained
                      • Oct 2017
                      • 45

                      #11
                      Not a real pitfall, but something to be aware of - I chose the Alexander Arms 18" barrel, which IMO looks beautiful (haven't shot it yet, I'm sure others can comment on accuracy), but the muzzle threading is 9/16" which _severely_ limits your muzzle device options. Looks like 5/8" threading is much more common. Just a friendly PSA.

                      Comment

                      • LRRPF52
                        Super Moderator
                        • Sep 2014
                        • 8569

                        #12
                        Biggest sidetracks I've seen:

                        Trying to mix and match parts based on the "best deal" you can get, instead of doing it right the first time.

                        I recommend getting a barrel/bolt combo from a reputable company who has learned the ins and outs of Grendel, or take the advice from the barrel maker as to what bolt they will be using.

                        I've had nothing but success across many builds now using SAAMI chambered barrels from AA, PF, Lilja, Satern, Criterion (PF), Specialized Dynamics, using real Grendel bolts with the .136" face depth and 2.810" OAL.

                        If you see the terms "Type 1 or 2", that was something started by BHW to keep track internally of different bolt face depths they were using from the days when people figured they could use the afterthought 7.62x39 bolts that many shops started cranking out as x39 began to gain popularity with hunters, plinkers, and machinegun shooters.

                        I'm using several Maxim bolts made for PF that were nitrided, and they just run and run for me without issues.

                        I also have an old AA barrel/bolt combo that has run for thousands of rounds without issue.

                        I'm very much enjoying my LaRue Stealth 2.0 complete rifle. You can build your own with their kits using all parts made under the same roof that have been designed and tested to work together.

                        For the home builders, biggest mistake I see is mis-aligned gas ports along the bore axis, not just cant. This causes short-stroking. Gas blocks aren't sealed up well either, so leakage allows gas to escape around the block, from the gas tube channel, and then carbons up to pressurize the system better. People will get their rifle dialed-in they think, then it will behave differently once it carbons up.

                        In general, seeking the cheapest possible parts is the start of a cascading effect that often results in a non-functional firearm, especially for those who are relatively new to the AR15. Cheap or incorrect length firing pins with softer tips will crater or deform, causing piercing or primer cutting. I've seen this several times now. All parts are not made equally, and many that people assume are made to the Mil-Spec are nowhere near it, including the Firing Pin, cam pin, carrier, carrier key, springs, detents, receivers, you name it.

                        Once everything is together, magazine troubleshooting is another potential hiccup area. Start with 1 round to determine bolt hold open. Then do 2, then capacity. Tolerance stack between lower receiver mag catch location, upper/lower fit, and the magazine can present problems since people are sourcing parts from so many different locations.

                        I also see a lot of people instantly go to adjustable gas from the start, when it usually isn't necessary. Especially on RLGS, you won't need it most of the time.

                        One big thing I've seen from several barrel makers is the use of excessively large gas ports on MLGS 18" barrels especially. That port should be .076", but I've seen a lot of .094" ports on them instead, which will not be timed well in most cases (excessive cyclic rate, FTExtract malfs, violent carrier movement and buffer rebound/stovepipes). If you do have a MLGS 18" or even 16" with a .094" port, choke it with adjustable gas.

                        Another problem is upper receivers with faces that aren't square. This can lead to early bolt lug fatigue even in 5.56 and will cause poor accuracy.
                        Last edited by LRRPF52; 12-02-2017, 02:59 PM.
                        NRA Basic, Pistol, Rifle, Shotgun, RSO

                        CCW, CQM, DM, Long Range Rifle Instructor

                        6.5 Grendel Reloading Handbooks & chamber brushes can be found here:

                        www.AR15buildbox.com

                        Comment

                        • zcostilla
                          Warrior
                          • Aug 2017
                          • 110

                          #13
                          Originally posted by LRRPF52 View Post
                          Biggest sidetracks I've seen:

                          Trying to mix and match parts based on the "best deal" you can get, instead of doing it right the first time.

                          I recommend getting a barrel/bolt combo from a reputable company who has learned the ins and outs of Grendel, or take the advice from the barrel maker as to what bolt they will be using.

                          I've had nothing but success across many builds now using SAAMI chambered barrels from AA, PF, Lilja, Satern, Criterion (PF), Specialized Dynamics, using real Grendel bolts with the .136" face depth and 2.810" OAL.

                          If you see the terms "Type 1 or 2", that was something started by BHW to keep track internally of different bolt face depths they were using from the days when people figured they could use the afterthought 7.62x39 bolts that many shops started cranking out as x39 began to gain popularity with hunters, plinkers, and machinegun shooters.

                          I'm using several Maxim bolts made for PF that were nitrided, and they just run and run for me without issues.

                          I also have an old AA barrel/bolt combo that has run for thousands of rounds without issue.

                          I'm very much enjoying my LaRue Stealth 2.0 complete rifle. You can build your own with their kits using all parts made under the same roof that have been designed and tested to work together.

                          For the home builders, biggest mistake I see is mis-aligned gas ports along the bore axis, not just cant. This causes short-stroking. Gas blocks aren't sealed up well either, so leakage allows gas to escape around the block, from the gas tube channel, and then carbons up to pressurize the system better. People will get their rifle dialed-in they think, then it will behave differently once it carbons up.

                          In general, seeking the cheapest possible parts is the start of a cascading effect that often results in a non-functional firearm, especially for those who are relatively new to the AR15. Cheap or incorrect length firing pins with softer tips will crater or deform, causing piercing or primer cutting. I've seen this several times now. All parts are not made equally, and many that people assume are made to the Mil-Spec are nowhere near it, including the Firing Pin, cam pin, carrier, carrier key, springs, detents, receivers, you name it.

                          Once everything it together, magazine troubleshooting is another potential hiccup area. Start with 1 round to determine bolt hold open. Then do 2, then capacity. Tolerance stack between lower receiver mag catch location, upper/lower fit, and the magazine can present problems since people are sourcing parts from so many different locations.

                          I also see a lot of people instantly go to adjustable gas from the start, when it usually isn't necessary. Especially on RLGS, you won't need it most of the time.

                          One big thing I've seen from several barrel makers is the use of excessively large gas ports on MLGS 18" barrels especially. That port should be .076", but I've seen a lot of .094" ports on them instead, which will not be timed well in most cases (excessive cyclic rate, FTExtract malfs, violent carrier movement and buffer rebound/stovepipes). If you do have a MLGS 18" or even 16" with a .094" port, choke it with adjustable gas.

                          Another problem is upper receivers with faces that aren't square. This can lead to early bolt lug fatigue even in 5.56 and will cause poor accuracy.
                          THIS is EXACTLY the kind of info I was hoping to find. I have 20 years of military service, so not new to the AR platform at all; and this is my second AR build, but I had no idea what I was doing the first time, and a friend who is a gunsmith helped me build it. (I sold it without really getting to get it set up exactly right because I had a bill to pay and chose to sell an asset I stead of going into debt).

                          I really wanted a 20” for a RLGS, but couldn’t pass up a Bear Creek Arsenal 18” Cyber Monday sale for under $60. I ordered a stripped bolt for another $19 and they said they’d make sure it was headspaced. I’ll be using MILSPEC bolt parts for reliability. I was unaware of the port sizing issues, so I’ll DEFINITELY take it to heart. I knew people were recommending adjustable gas blocks for mid-Length barrels but never knew exactly why. As soon as the barrel arrives I’ll measure it with a dial caliper to plan accordingly. I haven’t selected a BCG yet, but I’ll keep it standard weight. I do have a standard rifle length buffer tube and standard rifle buffer. I was planning on 10-round AA magazines, because of AA’s reputation for reliability. For what this rifle will be used for, I don’t need more capacity. Anything else I might have missed?
                          Last edited by zcostilla; 12-02-2017, 04:54 AM.
                          -Zac

                          Husband, Father, Veteran. Grateful for my redemption.

                          Comment

                          • grayfox
                            Chieftain
                            • Jan 2017
                            • 4295

                            #14
                            As to the stripped bolt and adding to what '52 said, be sure to get a grendel 0.136 style extractor. A complete grendel bolt will of course have it on there but you're saying a stripped bolt... don't use a 7.62x39 or even a 5.56 extractor, their groove etc dimensions differ from what you need in the Grrrr. There are some threads on this and even a couple of pics, I'll see if I can track them down.

                            this sticky has good details. Remember, grendel extractor for 0.136 depth boltface.

                            Guys, I've created an infographic to try and show the issues involved in using either a 0.136- or 0.125-inch bolt-face depth in 6.5 Grendel ARs. If you assume the extractor is the same overall length and has the same extractor pin location as a standard 5.56 extractor, then a 0.125 bolt-face depth requires a weakened extractor


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                            Custom AR-15 Rifles, Custom Uppers, Custom Lower, 6.5 Grendel, AR15, AR 15, AR-15, AR15 upper, custom upper, Lilja, DPMS, Precision, Precision Firearms, Precision-firearms, percision firearms, custom upper, custom ar, custom ar15, barrels, rifle barrels, Shilen, CAA, Command Arms, Yankee Hill, Yankee Hill Machine, 204 ruger, .204 ruger, 223 wyld

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                            (note the specific 0.136 face depth)
                            Last edited by grayfox; 12-02-2017, 02:00 PM.
                            "Down the floor, out the door, Go Brandon Go!!!!!"

                            Comment

                            • pinzgauer
                              Warrior
                              • Mar 2011
                              • 440

                              #15
                              Well, for one thing... Bolts don't set headspace. Barrel extensions do. The bolt is either in spec or it's not. Headspace is set on a jig when the barrel is set up and pinned. So if it's not right, it's the barrel.

                              Once headspace is set up, the gas port is drilled. So hopefully it will be in alignment. You won't be able to tell until you assemble it to the upper.

                              I hope your barrel and bolt combination works great, but as myself and others have mentioned, if it's your first Grendel build I would start with a known good barrel and bolt combination from the same manufacturer.

                              And if you do that in most cases the gas port will be the right size and there's no need to run an adjustable gas block. Which eliminates a whole nother round of things to tune.

                              I have a 16in Alexander Arms mid-length Barrel bolt combination. Runs perfectly on both carbine receiver extensions with an H buffer or on rifle.

                              I want to shoot, not spend weeks debugging an unknown combination.

                              There's nothing wrong with taking advantage of a $60 Barrel deal. It's just not something I would have started with for an initial Grendel build, and I certainly wouldn't start with the stripped bolt.

                              Make sure and use an M16 bolt carrier. There is no reason to use lighter, and you can get very good ones inexpensively from places like toolcraft. I bought their complete 556 bolt carrier groups nitrided and just swap out the Grendel bolt. And keep the 556 bolt as a spare for other rifles. I believe they were selling complete Grendel bolt carrier groups recently as well very competitively. ($69-89?). If you're not familiar, toolcraft has the contract to supply bolt carriers to DOD.

                              Pay attention to weather the barrel extension and your upper receiver have the same feed ramps, that's common, gotcha.

                              Hopefully it'll all play well together, and and even if you have to swap some things it's usually not complicated.

                              Rifle receiver extension is very forgiving. If you go carbine I would be inclined to go with a heavier buffer like an H or an H2. But that will depend on your gas pork. But it should work either way, that's just tuning

                              I would definitely beg borrow or buy some known good magazines since you're starting from scratch. I'm leaning towards the E-Landers from AA lately. Have a whole Fleet of older C products that have all worked perfectly, but I'm less confident of the newer ones and don't care for the asc's.

                              But my grendels will feed five rounds from pretty much any magazine including 556 magpulls. I have a couple of 20 round see product and Alexander Arms Grendel mags that I used, but for bench work a lot of times I use Magpul twenties if I'm only loading 5 rounds at a time.

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